In recent years, development of an electroluminescent element using an organic thin film (i.e., organic electroluminescent element) has been made. As a method for forming an organic thin film in the organic electroluminescent element, there are illustrated, for example, a vacuum deposition method and a wet film formation method.
The wet film formation method has such advantages as that it does not require a vacuum process, that it facilitates increase in size, and that a plurality of materials having various functions can be incorporated in one layer or in a coating solution for forming the layer. However, the wet film formation method has a difficulty in forming multiple layers. Therefore, elements produced by the wet film formation method are inferior to elements produced by the vacuum deposition method in driving stability, and have not reached a practical level with a few exceptions. In particular, although formation of two layers is possible by using, for example, an organic solvent and an aqueous solvent, formation of three or more layers has been difficult.
In order to solve such problem in forming multiple layers, patent documents 1 and 2 have proposed polymers (Q-1) and (Q-2) having fluorene rings and cross-linkable groups, wherein it is disclosed that multiple layers are formed by utilizing the fact that a network polymer obtained when these cross-linkable groups are reacted is insoluble in an organic solvent.

Also, patent documents 3 to 5 have proposed to use a triarylamine-containing polymer having a methylene group in the main chain thereof for an electrochromic element, an electroluminescent element, or for an electrophotographic photoconductor. In particular, patent document 4 discloses to use a polymer (Q-3) for a hole-transporting material in an organic electroluminescent element.
